Saturday, 26 December 2015

Light Tank M2A4: Catching Up

The American M2A4 light tank surpassed the stereotype that American interbellum tank building lagged behind European levels. It was mobile, well armed, and well protected. Work on this vehicle began more than a year before WWII and resulted in one of the best light tanks of its time.

Return of the cannon

There is an opinion that the Americans missed out on tank development in the interbellum years and were not ready for war. In reality, American tank designers kept track of what was happening in the world while they went their own way. Their specific theater of war needed specific vehicles. They had to be fast, and instead of a cannon, use two coaxial machineguns, one of which was high caliber. This was enough in order to fight light tanks and armoured cars of the era. The Americans embraced this concept in the mid 1930s. Price was another important factor. One of the reasons why Christie's proposal was rejected was because a light tank with the same armament, speed, and armour cost half as much.

Serious changes in American tank building were triggered by the same events as changes in Soviet tank building: the Spanish Civil War. This was the first war that saw the full spectrum of anti-tank measures, including high caliber machineguns. The 16 mm of front armour on American tanks reliably protected them from rifles, but was useless against high caliber machineguns. The M2A3 that appeared in 1938 had 22 mm of front armour, but the military knew that it was a band-aid solution.

The first person to raise the question of changing the definition of a modern tank was Lieutenant Colonel Gladeon M. Barnes, a key figure in American tank building. Barnes had many inventions to his name. He started in artillery, but began working on tanks in the 1930s. Barns worked on perfecting the Christie suspension: the idea of positioning the springs at an angle belonged to him. In 1936, Barnes patented the torsion bar suspension, which would appear on American tanks 7 years later.

After John Walter Christie lost the army's favour, Barnes became the main competitor of Harry Knox and Major John Christmas, who held a monopoly on suspensions for American tanks. Barnes was a serious adversary for Knox and Christmas since he, unlike Christie, was a high-ranking military man (Major General by 1943). In 1938, he also headed the design bureau at the Bureau of Ordnance.

Barnes thought that a new generation light tank should be armed with a 37 mm gun and have 38 mm (1.5 inches) of front armour. If such a tank used automotive components and was produced in large amounts, it could cost $20,000. The potential tank was designed with no turret, but the overall direction was correct. This happened in April of 1938, almost a year and a half before the start of WWII, so accusing the Americans of doing nothing until the start of the war is rather improper.

Christmas and Knox

The ball was in Christmas and Knox's court. In July of 1938, Christmas proposed two draft projects. The first was more of a conceptual vision of what a tank that used automotive components could look like. Two 8-cylinder Buick engines were proposed, with a combined power of 280 hp. The engines would be placed in parallel, connected with individual drivetrains with the frontal transmission. This layout forced the removal of the hull gunner, and the driver was positioned in the center.

Despite the fact that this design had obvious drawbacks, Christmas managed to get it produced in metal. The tank, indexed Light Tank T6, was produced in June of 1939. It is notable that this was the first American tank to use large-scale casting. The transmission cover and final drive covers were both cast, this later became a signature solution of American medium tanks. As for the layout with two engines, it was later used on the M5 and M24 light tanks, as well as the M3A3, M3A5, and M4A2 medium tanks.

The second draft was far more interesting. As the first variant, it had a suspension with three road wheels per side, but the rear idler was lowered to the ground, effectively increasing that number to 4. As with the Light Tank T6, this design was equipped with horizontal springs. The engine of the 10.5 ton tank was the same as that of the M2 light tank, a radial Continental W-670 engine with aircraft ancestry. The main feature was a one-man turret with a 37 mm gun and a coaxial Browning M1919 machinegun. This layout seemed a lot more promising.

A lecture hall for American tankers

The reality was a lot more practical than any drafts. According to the decree of the OCM #14844 issued on December 29th, 1938, the new tank was not built from scratch. Instead, the last built M2A3 was used, with serial number 321. The conversion was made at Rock Island Arsenal, where American tanks were made before the war. No changes were made to the suspension. The hull of the tank was minimally changed, with only a change to the engine compartment and the addition of a machinegun by the driver.

The turret was made from scratch. The idea of a one-man turret was discarded, and it was enlarged to fit two people. There were no seats in the turret, the commander and loader had to stand. A driveshaft connected the rear engine and front transmission, which the tank crew had to step over. The armour of the turret was 25 mm thick, same as the hull. This reliably protected the tank from high caliber automatic weapons.

The first prototype of the M2A4 light tank was sent to Aberdeen on May 11th, 1939. After a series of trials, a series of corrections was composed by the Bureau of Ordnance. A commander's cupola was added  with observation devices along its perimeter. The idea of an additional hull machinegun was approved, and another one was added on the right.

The gun, a tank version of the 37 mm AT gun designed by Gladeon Barnes, also demanded changes. The barrel was shortened by 13 cm to reduce the risk of damaging it while driving in a forest. Another significant change was the addition of an armoured cover for the recoil mechanism. Brackets were welded onto the front of the tank to cause bullets and small fragments to ricochet. A vehicle with all these changes returned to the proving grounds in October of 1939. As a result of these trials, the M2A4 was approved for service.

The first mass production M2A4 was produced in May of 1940. It's worth noting that before the M2A4, American tanks were built at the Rock Island Arsenal. The main producer of this new vehicle was American Car & Foundry Company. The majority of M2A4 tanks were assembled here, 365 in total. Another 10 were built in April of 1941 at Baldwin Locomotive Works. Late production vehicles received an improved gun mantlet, and a portion of the tanks were equipped with Guiberson T-1020 diesel engines.

The age of the Light Tank M2A4 was not long. In March of 1941, production of the superior Light Tank M3 began, better known by the name "Stuart", given to it by British tankers. Nevertheless, despite falling in the shadow of its younger brother, the M2A4 was an important step for American tank building. The characteristics of the tank were among the best in its class. They were close to those of the Czechoslovakian LT vz. 38, while superior in mass and speed. Due to its powerful gun, the M2A4 could fight almost any tank of the era. All tanks of this type were equipped with radios, a very important feature. Additionally, like other members of the M2 family, the M2A4 was very fast, reaching a speed of 58 kph. Few tanks of the era could manage such a feat.

Like other M2 series tanks, the M2A4 was somewhat of a learning instrument for American tankers. It was the main participant in large exercises held to work on combat action. In summer of 1941, these tanks began being replaced with the superior Light Tank M3, but the M2A4 remained in training until until the end of 1942.

These tanks were the first that the United States sent out as a part of the Lend-Lease program. In early 1941, 36 tanks were sent to Great Britain. Since code names were given in the spring of 1941, the M2A4, unlike the Medium Tank M3, did not receive a proper name. This tank was used, in part, by the 9th Queen's Royal Lancers while the regiment was located in England in the summer-fall of 1941. These tanks did not see combat, as the first Stuart I tanks started arriving in the spring of 1941. There is information that the 7th Tank Brigade received these tanks in 1942 and used them in Burma, but it has not been confirmed.

Unlike the British, the Americans used the M2A4 in battle. The Marine Corps, traditionally equipped with hand-me-downs, received 36 M2A4s. The 1st Tank Battalion attached to the 1st Marine Division fought at Guadalcanal. The battalion had a rather heterogeneous composition: A company had M2A4 and M3 tanks, while C company managed to receive new M3A1 tanks.

The battalion landed in Guadalcanal in August of 1942. During battle, the light tanks showed themselves equally well. The M3 and M3A1 were superior designs and had improved armour, but in practice, the M2A4 proved equivalent. The battle of Guadalcanal was very unusual in the sense that American and Japanese tankers did not fight each other, but enemy AT guns and infantry. The 1st Battalion fought here until January of 1943.

One M2A4 light tank survived to this day, from the A company of the 1st Tank Battalion. This tank was bogged down in a swamp during the battle for Henderson Field in October of 1942. The M2A4 spent nearly 70 years there, until a private collector recovered it in 2009. According to available information, the tank is partially restored, and might one day be functional again. Since the M2A4 has a significant number of parts in common with the much more common M3 and M3A1, this is a very possible outcome.

The Light Tank M2A4 ended up in the shadow of its more numerous brother, the Light Tank M3. Nevertheless, it became the first truly modern American tank, matching or even surpassing foreign competitors. Only luck pulled it off the stage so quickly.

Original article by Yuri Pasholok.

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